Sharif Digital Repository

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method for simulation of fluid flow. Movable particles are used to interpolate fluid properties instead of fixed Eulerian grids in this method. By essence, the aforesaid particles are movable points which carry the fluid properties such as temperature, enthalpy, density, etc. these variables can also be the stress, strain or the rheological properties of the fluid. Thus, this method needs no grids and the fluid properties are calculated using an interpolation mechanism which classifies this method as meshless. A computational code is designed using SPH for the simulation of multiphase flows. Usage of the Lagrangian formulation has made it... 

The heavy ion collision experiments are in progress in order to investigate how the Universe has evolved after the Big Bang. The recent observations show that a nearly perfect fluid is produced after heavy ion collisions. An appropriate incorporation of the relativistic hydrodynamics and the field theory would help us to describe the dynamics of QCD (Quantum Chromodynamics) matter under extreme conditions, and to survey the expected phase transitions. The majority of efforts to investigate the characteristics of the QCD plasma are devoted to an ideal, non-dissipative one. To get the results which are highly in accordance with the experiment, it is necessary to bring also in mind the role of... 

Smoothed Particle Hydrodynamics(SPH) is the oldest Lagrangian method for solving fluid equations. Fluid is approximated with particles that represent a control mass and carry physical properties su as mass, temprature and . . . Simpler formulation relative to other methods like finite volume and finite element, no need for surface traing and ease of adding new physics are benefits of this method. In this method it is necessary to find neighboring particles that are closer than smoothing lenght (h) for ea particle. is is a time consuming operation causing SPH to be a computationaly expensive method. First simulation of Power-law fluids is considered. It has been observed that using of... 

Planing crafts in waves are characterized by large and violent vertical motion and acceleration. The hull structure is subjected to high impact loads and the crew experiences high transient vertical acceleration and in most cases the crew needs to lower speed in order to avoid damage to the hull.In recent years, interest on increasingly faster marine vehicles has remarkably grown. Typical planing monohulls are: patrol vessels, pilot boats, rescue vessels, coast guard vessels and small navy vessels. So the behavior of planing monohulls in waves has been a widely researched topic since more and more planing monohulls appeared.The accurate prediction of large amplitude ship motions in severe... 

Flows which density difference in a gravity field is their driven force are called Density Currents. Such flows are present in both nature and man made environments. Due to their importance, there have been large efforts to analyse them in both experimental and numerical way. In the present thesis, Smoothed Particle Hydrodynamics (SPH) is introduced as a new tool to simulate such flows. As the method is Lagrangian and particle based, simulation of Density Currents with particles can be addressed more naturally that can be accounted as the method preference to traditional mesh based methods. SPH projection method is incorporated to impose incompressibility. To precisely simulate Density... 

A finite volume algorithm to assess hydrodynamic aspects of a rigid and up to three degrees of freedom marine structure in the context of transient two-phase flow o viscous incompressible fluids is presented. Different components of the algorithm are selected just after a complete review of all probable choices. Using a collocated arrangement to save data, a fractional step method is applied to satisfy Navier-Stokes and continuity equations, as an appropriate choice in transient flows. Also, a volume fraction transport equation is solved to capture large and complex deformations of the interface between two phases. So, an effective fluid is introduced by combining two immiscible phases in... 

One of the utmost important factors during salvage operation of drowned ships is raising velocity. Uncontrolled raise is a dynamic phenomenon which can lead to the sudden tensions, collapse in airbags or ships. Studing this issue helps the engineers which kinds of problems are more important during salvage operations. This study focus on modeling and analysis of raising movment of the ship with FLOW-3D and ABAQUS software.
In FLOW-3D environment, hydrodynamic analysis of rising movment of drowned ship has been done. We should mention that applied forces and velocities and other parameters from the FLOW-3D output should be passed IMCA Criteria to avoid uncontrollable raise. In ABAQUS... 

The number of discovered extrasolar planetary systems has increased immensely during the past 15 years. The various outcomes of planetary formation are a result of the complicated interaction between gravitational, hydrodynamical and accretion processes a considerable amount of which is not yet understood. Thus far the effect of a planet embedded in a protoplanetary disk has been studied both analytically and using numerical simulations. These suggest that under suitable circumstances tidal effects result in the formation of a gap in the disk about the orbit of the planet. This result has been particularly used to detect massive extrasolar planets (massive enough to form gaps).In this study... 

Ship maneuverability is so important from different aspects. According to the regulations of International Maritime Organization (IMO), every vessel has to meet the minimum requirements of mentioned rules. Consequently, prediction of ship maneuverability in early stages of the ship design has become to one of the most necessary steps for shipbuilding and design companies. In this research work maneuvering of a high speed ship has been investigated using three different propulsive modes, considering propeller and rudder systems, azipod propeller and waterjet systems. First of all, hydrodynamics equations of each cases while considering different motion modes such as surge, sway, yaw, and roll... 

Nowadays, because high global demand for energy has led to the extensive use of fossil fuels with numerous unintended consequences such as air pollution and greenhouse effect, research and development around optimization of energy infrastructure has become much more important. Consequently, many scientific approaches have been applied to replace fossil fuels with renewable natural energy resources. One of the renewable energy types that fewer papers have been published about it, is the enormous energy of Marine currents. The origin of this energy is mostly tidal effect, or ocean currents that are available in most of oceans and seas around the planet earth. The most important criteria for... 

Trombosis formation in blood flow is a complex biochemical and very important process for body health which impedes blood loss by creating obstacles in the path of injured wall vessels. Although this phenomenon plays a very significant role in healthy body function, unfortunately it has been observed that it could cause diseases or even stroke. The reason is that thrombosis formation in blood and its detachment from the vessel wall can result in block body capillaries and lead a catastrophic event for the body. One of the factors which motivates blood for forming unnatural thrombosis is the vessel stenosis. It would ange in normal blood flow path and cause thrombosis formation as time is... 

In the present study, synthesis, preparation, and application of bimetallic iron/nickel nano-particles were experimentally investigated with the aim of groundwater remediation. Firstly, iron/nickel nano-particles were synthesized according to chemical reduction and stabilization with starch biopolymer, and then characterized. Results confirmed the formation of bimetallic iron/nickel nano-particles with mean size of 75 nm that starch placed around of them. The more stability characteristic and also enough mobility ensure their diffusion through porous media. Secondly, reactivity of synthesized nano-particles for removal of various contaminants including nitrate, chromium, and lead were... 

In the present study, the simulation of incompressible Electro-Magneto-hydrodynamic flows is performed using a finite volume lattice Boltzmann method (FVLBM). The Boltzmann transport equation is solved using a cell-centered finite volume method on structured meshes. A central difference scheme is used to discretize the spatial derivatives and the fourth-order numerical dissipation term is added to stabilize the solution. To discretize the temporal derivative, the fourth-order Runge-Kutta time stepping scheme is applied. The standard collision-streaming lattice Boltzmann method has been used to simulate EMHD flows in the literature, however, it has several deficiencies such as the... 

In this thesis an SPH method is used for simulating multiphase two- and three-dimensional Newtonian fluid flows. The weakly compressible algorithm consists of two steps of prediction and correction. In the prediction step, the velocity field is integrated forward in time without enforcing incompressibility. The correction step consists of enforcing incompressibility by solving the pressure Poisson equation which creates a trade-off between the pressure and density variations. The surface tension force is applied in the linear momentum conservation equation by the divergence of the surface stress tensor. Advanced techniques are applied to achieve better convergence and reduce pressure-related... 

Study of two-phase flowin porous media forms a basis for investigating various fluid systemsin the nature and industries. In recent years, more and more researchers use pore-scale mod-els to explore various physical phenomena occurring in complex media such as hydrocarbonreservoirs. After solving the flow equations in pore-scale, this approach can be utilized tocalculate some macroscopic values using particular forms of averaged flow field.In this research, Smoothed Particle Hydrodynamics (SPH) is used to simulate two-phaseflow in pore spaces of two- and three-dimensional porous media. The SPH method is a La-grangian meshless method that is suitable for flows with free surfaces, deformable... 

Autonomous underwater vehicles (AUVs) are a type of marine vehicles which are currently being used for exploration, maintenance, repairing of marine structures and military appliances. Unmanned underwater vehicles categorize in two types: ROVs and AUVs, ROVs (remotely operated vehicles) usually are connected to the mother vessel with a cable, conduction signals transfer through this cable and there is an operator in the control loop. The vehicle may be fed up with this cable, AUVs are modern underwater vehicles which the operator on controlling and conducting is removed, there is no connection between the vehicle and mother vessel, energy sources and controlling orders are set up in the... 

Relativistic hydrodynamics and kinetic theory are often used to analyze the experimental data from heavy ion collisions. One of the most important observations is the anisotropy in the number density of the detected particles after the collision in the longitudinal and perpendicular directions with respect to the reaction plane. On the other hand, very strong magnetic fields are created during the early stages of non-central heavy ion collisions. The presence of constant background magnetic fields, aligned in the perpendicular direction to the reaction plane, can be one of reasons for the aforementioned anisotropy in the number density of detected particles. In this thesis, we study the... 

During the drilling process, cutting concentration in vertical and inclined wells is a common problem and major issue in designing hydraulic parameters. This is becoming more important in near bit area. Cutting transport usually is affected by several parameters such as mud rheology, flow rate, nozzle size, rotation speed, and mud weight.
In this work it was aimed to design a new set-up to test all the factors on hole cleaning phenomenon especially in near bit area. The set-up consists of a 16 feet long flow loop, 3.28 feet height of the test section, and 3.33 inches inner diameter of the test section. Each parameter which has an impact on hole cleaning could be varied. The cutting... 

Atomic force microscopy (AFM), as an indispensable tool for nanoscale characterization, has major drawback for operation in a liquid environment arising from the large hydrodynamic drag on the vibrating cantilever. The newly introduced “Trolling Mode” (TR-Mode) AFM resolves this complication utilizing a specialized nanoneedle cantilever that keeps the cantilever outside of the liquid. Herein, a mechanical model with a lumped mass was developed to capture the dynamics of such cantilever with a nanoneedle tip. This new developed model was applied to investigate the effects of the needle – liquid interface on the performance of the AFM, including the imaging capability in liquid. Also... 

Nowadays, autonomous underwater vehicles (AUVs) are implemented to carry out various activities under water. Amongst applications of these vehicles we can mention monitoring of marine creatures, mine installation and neutralization, and many military applications. The objective of this research is designing a control algorithm for underwater vehicles such that an under actuated vehicle can reckon a moving target as a reference and whilst chasing it, vehicle can keep a fixed distance from this target. First the dynamics of underwater vehicles are modeled and in this modeling different effects due to under water motion such as drag force, buoyancy force, and also added mass are included...